Arduino Due clone based on the Atmel SAM3X8E, KiCAD design

This project is about designing a PCB for the Atmel SAM3X8E with the Open Source layout editor KiCad [1]. The result is a kind of Arduino Due Clone, since the MCU is the same and I also have tried to get a similar pin mapping.

I have until now designed quite some PCBs with Eagle [2] from CADSoft and was happy with the software. But since my designs are getting more and more advanced, I start to get limited by the 8 cm x 10 cm size limitation in the light version. The Hobbyist version would increases the size to 16cm x 10 cm for around 169$. Further it would be nice if one could move around a set of tracks, when a little bit of space is needed for another track. In Eagle one has to move every track individually.

Looking around for alternative PCB software, which does not have these limitations, I found KiCAD, which had improved in the last time, since developers at CERN started to take part in the development [3]. With the support of CERN, KiCAD will have a big future. Already now it goes in the direction of ALTIUM, even if it is not yet there.

Features which made KiCAD interesting for me:
* Hierarchical Schematics
* Unlimited size and many signal layers
* Push and Shove router
* The whole editor makes a very professional impression
* More flexibility in the designs

So I believed in KiCAD and started with the schematic design.

The schematics sheet with the micro-controller is shown in the next figure.
The whole schematics can be viewed as a pdf Schematics

After the schematics comes the layout of the PCB. This went very smooth after getting used to the key combinations and functions available. One announcing thing are the different render modes, providing different functionality.
But I expect this to be more uniform in the future.

In the design rules I allowed the following minimal settings:

Clearance

8 mil

Minimal Track Width

10 mil

Minimal Via Pad Diameter

40 mil

Minimal Drill Diamter

0.45mm

These are the limits what I’m able to fabricate at home with my etching process.

At the end the PCB looked the following:

Very nice is the export of the PCB from KiCAD into a PDF for printing on a transparency.

The two layer PCB was exposed on my light board, developed and etched. Via holes were drilled, small silver wires are pressed into the holes as described in Flat VIAs for double sided PCBs and the whole PCB was tinned as described in PCB tinning including VIA soldering.
The vias which are not under the IC were additionally solder for better/saver contact. Holes for the through hole parts were drilled and the PCB was soldered.

For those who wonder why the USB-B contact is on the wrong side, this is due to an error of the footprint in KiCAD.
This issue is fixed in Rev 2 of the PCB (not etched yet).

I simply connect a FT232RL USB to Serial adapter to the board via the 5V_Serial pins. Then cyou get a std serial port you can use to program with the Arduino IDE. Have a look on EBAY there you can buy them for a small amount of money and can reuse them for all kinds of projects.

I like this design a lot I think I will try to compile this open source hardware in macrofab that way it can improve and can be added to other open hardware projects and grow, like open source software. OpenHardwareEXG I know can use a due so if that compiles correctly I will compile this one I can email the files I create to add to gethub if I can get macrofab to compile it.

If I remember well, the official Arduino Due move th Pa29 pin to one of the external connectors.
If I build your clone, I don’t need any additional bootloader than the SAM-BA one, and I can start to design .ino files from the scratch using the Arduino Ide?